1: With manganese(IV) oxide in dichloromethane T=0 - 20°C; 2: With pyridinium p-toluenesulfonate in ethanol T=50°C;

1.1: n-butyllithium / tetrahydrofuran / -78 - 20 °C 2.1: manganese(IV) oxide / dichloromethane / 0 - 20 °C 2.2: 50 °C View Scheme

1.1: toluene-4-sulfonic acid / dichloromethane / 20 °C 2.1: n-butyllithium / tetrahydrofuran / -78 - 20 °C 3.1: manganese(IV) oxide / dichloromethane / 0 - 20 °C 3.2: 50 °C View Scheme